Use of proteases to reduce steep time and SO2 requirements in a corn wet-milling process

To eliminate the diffusion barriers associated with enzyme addition during conventional steeping, we have developed a two-stage milling procedure to evaluate the effects of enzyme addition on corn wet milling. The current study compares the effects of the addition of commercially available enzyme preparations during conventional steeping to their comparable addition in the two-stage procedure. Results are presented in terms of yields of fiber, starch, germ, and gluten. The results demonstrate that the application of enzymes to the normal steeping step of wet milling is not an effective means of decreasing the steeping time or sulfur dioxide usage. Only when specific enzymes are added to the hydrated ground corn, using the modified two-stage procedure, are enzymes effective in decreasing the steeping time and sulfur dioxide requirements. The overall steeping time with the two-stage modified procedure ranges from 6 to 8 hr, representing a 67-83% reduction over the conventional process. The modified process greatly decreases, and possibly eliminates, the need for sulfur dioxide addition, while producing starch yields and quality equivalent to that from the conventional process.